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Old 09-04-2017, 09:30 PM   #1
Ross F-1
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Default Vacuum can for 48-53 GM-style distributors?

My 3rd Accel adjustable vacuum advance can just failed, it's a miracle if the damn things last 2 years. I want to run around 8 - 10 deg vac advance per Richard in FL/Ol Ron's testing. Is there a GM factory can that will provide close to that?

I'm running the MSD Ready-to-Run which uses the GM points-style vacuum can (non-HEI).

Couldn't find anything in a search, appreciate any help!
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Old 09-04-2017, 10:33 PM   #2
Ol' Ron
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Default Re: Vacuum can for 48-53 GM-style distributors?

Yes, there is a 10 deg GM can, Bubba might have the number. However, that might be alittle much, but thad depends on the mechanical advance. I onlly run 20 total at 2000. The reason is better low speed acceleration. Now that depends on the rest of the engine and a good AF meter. Do you have the adjustable Mechanical advance? Good luck.
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Old 09-04-2017, 10:35 PM   #3
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Default Re: Vacuum can for 48-53 GM-style distributors?

Ross, I found a site one time that had a listing of the GM vacuum cans with max advance and the vacuum that they reach it. I found one that gives 8 degrees at 8" of vacuum for my car. A quick look doesn't turn it up, but I'll keep looking.

Found it: http://outintheshop.com/faq/Vac%20Adv%20Spec.pdf

I used the VC1810, got it at Autozone (ordered). I think their number is DV1810.

Link: http://www.autozone.com/ignition/vac...rchText=dv1810

If you get a can with too much vacuum advance, I made an adjustable stop for one. Let me know if you want details.

Last edited by 40cpe; 09-04-2017 at 11:00 PM.
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Old 09-05-2017, 12:56 AM   #4
Ross F-1
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Default Re: Vacuum can for 48-53 GM-style distributors?

That's exactly what I needed, 40cpe! Many thanks! From the chart, the VC680 would have been my pick, the 1810 looks to be for heavily cammed engines? I am interested in your adjustable stop. I have a spot welder and was figuring that worst case I could add a stop, but it wouldn't be adjustable.

Ron, I am at high altitude, so I have been running with 2 deg additional static advance (4 deg total), which is common practice here to make up for thin air/low compression/less O2. Mech advance has lightest springs and bushing limiting to 18 deg, all in by ~1800. I do have the Innovate AFM installed and am all set as far as jetting. Also running the Rochester 2G which has a power valve that can be adjusted, which really helps.
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Old 09-05-2017, 07:44 AM   #5
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Default Re: Vacuum can for 48-53 GM-style distributors?

Ross, on the stop: I cut a piece of sheet metal just a little wider than the flat arm that goes into the distributor and about 1/4" longer than the distance from the screw at the end of the arm to beyond the slot in the arm that the round advance rod moves in. Cut two slots in the sheet metal stop wide enough for the holding screw on one end and the round advance rod on the other. You can scribe some reference marks on the sides so you can estimate how much to move it if you need to adjust. Slip the stop over the round advance rod before you install the vacuum can in the distributor and install. Adjust by loosening the screw and sliding the stop. I hope you can visualize what I attempted to picture for you. I also found that it is easier to cut the slots in a larger piece of metal and trim afterwards.

If you need a photograph, I'll pull my distributor cap later this morning.

I think it is also notable that when you block the upper end of the advance, you are using the beginning of the advance curve so your limited max vacuum advance will occur at less than the advertised max vacuum of the can. You might want to start with a can that takes a higher vacuum to start opening to compensate.

Last edited by 40cpe; 09-05-2017 at 07:55 AM.
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Old 09-05-2017, 09:23 AM   #6
Ross F-1
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Default Re: Vacuum can for 48-53 GM-style distributors?

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I see what you're saying, no picture needed. Good idea! When I get my new can I'll get after it. I understand your comment on the pull-in rating too, I'll have to think about that. Thanks again!
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